Detection of charge around a nanoparticle in a nanocomposite using electrostatic force microscopy

In this work, electrostatic force microscopy (EFM) is used to investigate the interface around a nanoparticle in terms of its properties viz. electric charge density and dielectric constant. Nanodielectrics composed of barium titanate (BaTiO 3 ) nanoparticles embedded in epoxy matrix are used for the study. Phase shift images obtained from EFM experiments indicate the region occupied by an embedded particle in the matrix, as well as the presence of an interfacial region around it. In an earlier work 12, a finite element method (FEM) based 3-D electrostatic model was developed by the authors to computationally obtain the EFM phase shift in the interfacial region, and was used in conjunction with experimental data to estimate the dielectric constant and thickness of the interface. The possibility of charge on the particle surface and/or in the interfacial region around it, is investigated using the same model and methodology. Computational results indicate that the presence, magnitude and polarity of charge affect the EFM phase shift signal. Comparison of computational and experimental data, confirms the presence of an interfacial region around the particle with a dielectric constant higher than that of the bulk epoxy, and with negative charge present in it.